The hypothesis of this trial is that live-attenuated varicella vaccine will be safe in VZV-naive, asymptomatic or mildly symptomatic HIV-infected children 1-8 years of age. The aim of this study is to evaluate the safety and immunogenicity of varicella vaccine in HIV infected children. The study will monitor the short-term local and systemic reactions following administration of live-attenuated varicella vaccine, and monitor the clinical and immunologic progression of HIV in children who have received varicella vaccine. Immunization against varicella should protect HIV-infected children from the risk of severe disease and life-threatening complications due to natural varicella infection. Current passive prophylaxis measures with VZIG therapy are suboptimal, because of the unpredictability of timely notification of the child's caretaker of exposures, as well as the need for repeated VZIG administration for each of the many exposures during the child's lifetime. Managing chickenpox exposures has become one of the most time-consuming, costly, and logistically difficult aspects of providing care to a clinic population of HIV-infected children. The study population is comprised of children between the ages of 12 and 48 months, with asymptomatic (P-1) or mildly symptomatic (P-2), perinatally-acquired HIV-1 infection,. In addition, a control group consisting of children 12-48 months old, with P-1 or mild P-2 perinatally-acquired HIV-1 infection who have had wild-type varicella infection will be registered. A total of 56 (36 treatment and 20 control) subjects will be enrolled.